The present invention relates to a method of producing an organic light-emissive device comprising an electroluminescent polymer.
Organic light-emitting devices typically comprise a layer of an electroluminescent polymer arranged between an anode and a cathode such that positive and negative charge carriers can move between the anode and cathode and the electroluminescent polymer layer.
Conventionally, the electroluminescent polymer layer is deposited by coating a substrate comprising the anode or cathode with a solution of the electroluminescent polymer or a solution of a precursor to the electroluminescent polymer layer followed by conversion of the precursor to the electroluminescent polymer. Coating of the substrate with such solutions is, for example, typically carried out using a spin-coating or blade-coating technique.
In the case that a patterned light-emissive layer is required, ink-jet printing has been used to selectively deposit a solution of the electroluminescent polymer or its precursor on selected portions of the substrate.
According to a first aspect of the present invention, there is provided a method of producing an organic light-emitting device comprising a patterned electroluminescent polymer layer arranged between two electrodes such that charge carriers can move between the first and second electrodes and the electroluminescent polymer layer, the method comprising the steps of (a) providing a substrate comprising the first electrode, (b) depositing solid particles comprising the electroluminescent polymer onto selected portions of the surface of the substrate, (c) securing to the substrate those solid particles comprising electroluminescent polymer particles deposited onto the substrate in step (b) to form the patterned electroluminescent polymer layer; and (d) forming the second electrode over the surface of the electroluminescent polymer layer opposite the first electrode.
The steps of depositing the solid particles comprising electroluminescent polymer onto selected portions of the surface of the substrate, and securing them to the substrate may be carried out by an electrostatic technique of the type used in electrostatic printing. Reference is made to xe2x80x9cElectromagneticsxe2x80x9d by John D. Kraus, McGraw-Hill Publishing Co. 1999 and xe2x80x9cElectromagnetics: with Applicationsxe2x80x9d by John D. Kraus, McGraw-Hill Publishing Co. 1999.
The patterned layer of electroluminescent polymer may for example consist of a two-dimensional array of pixels of one or more electroluminescent polymers.
The method preferably further comprises a step of selectively covering those portions of the substrate onto which the electroluminescent polymer was not deposited with an insulator material to form an insulating matrix around the pixels of electroluminescent polymer, wherein the insulator material is preferably also deposited as solid particles of said insulator material, which are then secured to the substrate.
The solid particles comprising the electroluminescent polymer preferably have a particle size of about 100 nm. The insulator material is preferably black.
According to a preferred embodiment of the present invention, there is provided a method of producing an organic light-emitting device comprising a patterned electroluminescent polymer layer arranged between two electrodes such that charge carriers can move between the first and second electrodes and the electroluminescent polymer layer, the method comprising the steps of (a) providing a substrate comprising the first electrode, (b) providing solid particles comprising the electroluminescent polymer and capable of supporting an electrostatic charge of a first polarity; (c) providing a transfer surface having portions which are independently capable of supporting an electrostatic charge and applying an electrostatic charge of a second polarity to selected portions of the transfer surface; (d) selectively transferring said solid particles comprising electroluminescent polymer to said charged selected portions of said transfer surface by virtue of an electrostatic interaction between said selected portions of the transfer surface and the solid particles; and (e) contacting the transfer surface with the substrate so as to transfer the solid particles held thereon to selected portions of the substrate and securing them to the substrate to thereby form a patterned electroluminescent polymer layer on the substrate; and (f) forming the second electrode over the surface of the patterned electroluminescent polymer layer opposite the first electrode.
The electrodes are preferably adapted such that selected portions of the patterned electroluminescent polymer layer can be independently activated.
In one embodiment, the second electrode is formed by applying a pre-patterned second electrode to the surface of the patterned electroluminescent polymer layer.